A remarkable legion of guests: Diversity and host specificity of army ant symbionts

Abstract

Tropical rainforests are among the most diverse biomes on Earth. While species inventories are far from complete for any tropical rainforest, even less is known about the intricate species interactions that form the basis of these ecological communities. One fascinating but poorly studied example are the symbiotic associations between army ants and their rich assemblages of parasitic arthropod guests. Hundreds of these guests, or myrmecophiles, have been taxonomically described. However, because previous work has mainly been based on haphazard collections from disjunct populations, it remains challenging to define species boundaries. We therefore know little about the species richness, abundance and host specificity of most guests in any given population, which is crucial to understand co‐evolutionary and ecological dynamics. Here, we report a quantitative community survey of myrmecophiles parasitizing the six sympatric Eciton army ant species in a Costa Rican rainforest. Combining DNA barcoding with morphological identification of over 2,000 specimens, we discovered 62 species, including 49 beetles, 11 flies, one millipede and one silverfish. At least 14 of these species were new to science. Ecological network analysis revealed a clear signal of host partitioning, and each Eciton species was host to both specialists and generalists. These varying degrees in host specificities translated into a moderate level of network specificity, highlighting the system's level of biotic pluralism in terms of biodiversity and interaction diversity. By providing vouchered DNA barcodes for army ant guest species, this study provides a baseline for future work on co‐evolutionary and ecological dynamics in these species‐rich host–symbiont networks across the Neotropical realm.

Dynamics of gut microflora across the life cycle ofSpodoptera frugiperdaand its effects on the feeding and growth of larvae

“…The study of insects and symbiotic intestinal microbes provides a basis for subsequent functional studies. 17,[20][21][22][23][24][25][26][27][28][29][30][31][32] The gut microbiome can be influenced by external environmental factors such as weather, temperature, and other factors such as antibiotics. [33][34][35] There were significant differences in microbial communities at different developmental stages of insects such as G. molesta, Heliothis virescens, Nilaparvata lugens and Zeugodacus tau.…”

Comparison of Gut Bacterial Communities of Fall Armyworm (Spodoptera frugiperda) Reared on Different Host Plants

“…In recent years, more insect microbial communities have been discovered and studied. Studies have been reported in honeybees [34][35][36][37], fruit flies [38][39][40], mosquitoes [41,42], Dectes texanus [43], and termites [44,45], as well as in lepidopteran pests, such as Grapholita molesta [18,[46][47][48], Carposina sasakii [46,47], and Cydia pomonella [47]. The gut microbial community of the honeybee has stable species and structure, and there are many unique microbial types in different regions of Apis mellifera.…”

“…Host specificity in biodiversity highlights the different degrees and interactive diversity across the levels of biodiversity in the system. Host digestion strategies define the structural and functional potential that drive the gut microbial community [44,45]. OTUs (operational taxonomic units) and species abundance were significantly different in different instars across the whole life cycle of G. molesta.…”

Structure of an ant-myrmecophile-microbe community

“…The nature of these interactions has in many cases evolved to become obligate, leading to extreme specialization of one insect species on a single or small number of partners (Beeren et al, 2021;Elmes, Barr, & Thomas, 1999;Hawkins, 1994;Komatsu, Maruyama, & Itino, 2009; López-Estrada, Sanmartín, Uribe, Abalde, & García-París, 2021; Maruyama & Parker, 2017;Strand & Obrycki, 1996). How such interspecies dependencies shape the evolution and composition of insect microbiotas remains an open question.…”

“…Although ruthlessly policed against intruders, colonies are vulnerable to exploitation by an array of specialized arthropods that have evolved ways to evade recognition and gain entry (Kistner, 1979(Kistner, , 1982Parker, 2016). Such organisms, termed "myrmecophiles", are often obligately dependent on a single host ant species (Beeren et al, 2021;Elmes et al, 1999;Komatsu et al, 2009;Maruyama & Parker, 2017). To infiltrate colonies, myrmecophiles commonly employ deceptive strategies that permit them to forge intimate relationships with their unknowing hosts.…”